Wednesday, February 19, 2014

PlatterSpeed Specs on LT-30 #1

[Update: all these numbers are mostly explained by off center wow, which is typically 10 times greater than good turntable wow, see the next post. There appears to be no serious problem with the LT-30 #1 after all. It measures no worse than my other turntables, in fact the Lenco which seems to sound the best measures the worst.]

frequency: 3150.2 Hz (excellent, strangely)

max deviation (raw) -0.39%/+0.38%

wow (DIN 2-sigma) +/- 0.12%

wow (DIN dynamic) +/- 0.08%

The wow is clearly dependent on platter angle, first it goes up, then it goes down, as the platter turns. It is very audible to me. The mean 3150 is strangely correct but the high is at least 3165 and the low is at 3135 (this is worst case in a 10-20 sec recording).

I would call this cogging to the extent that an entire pole or set of poles in the motor is working at significantly diminished capacity. When the platter position dependent component is removed, the resulting wow and flutter is quite small, with the maximum deviations being 3155 and 3145.

This is obviously a problem which needs to be repaired, and the turntable is basically useless until it is.